Issue 29, 2006

Star-shaped block copolymer stabilized palladium nanoparticles for efficient catalytic Heck cross-coupling reactions

Abstract

Palladium nanoparticles of improved stability against aggregation were prepared using 5-arm star-shaped block copolymers with a poly(ethylene oxide) (PEO) core and a poly(ε-caprolactone) (PCL) corona as templates. The PEO core of these star-shaped block copolymers could be swollen with palladium acetate (Pd(OAc)2) in N,N-dimethylformamide (DMF), and Pd nanoparticles were obtained by reduction with NaBH4. This procedure resulted in well defined Pd nanoparticles that were stabilized against aggregation due to a barrier of PCL chains. Transmission electron microscopy (TEM) experiments strongly suggested that one Pd nanoparticle was formed inside each star-shaped block copolymer. The stability of the Pd nanoparticles with respect to aggregation was strongly dependent on the length of the PCL chains. Subsequently, these nanoparticles were evaluated for their capability to act as catalysts in Heck coupling reactions. These reactions were performed in an automated synthesizer and monitored by GCMS revealing that these particles are highly active for the catalytic reactions mentioned. Up to 99% conversion was observed for the coupling of styrene with 4-bromoacetophenone within 24 h at a catalyst loading of 0.1 mol%.

Graphical abstract: Star-shaped block copolymer stabilized palladium nanoparticles for efficient catalytic Heck cross-coupling reactions

Article information

Article type
Paper
Submitted
20 Feb 2006
Accepted
02 May 2006
First published
05 Jun 2006

J. Mater. Chem., 2006,16, 3001-3006

Star-shaped block copolymer stabilized palladium nanoparticles for efficient catalytic Heck cross-coupling reactions

M. A. R. Meier, M. Filali, J. Gohy and U. S. Schubert, J. Mater. Chem., 2006, 16, 3001 DOI: 10.1039/B602548J

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